Extensible boom assembly

ABSTRACT

A truck-mounted boom assembly having a plurality of telescopic boom sections. Each boom section has right angle corner members secured to top, bottom and sideplates. Rockable friction pads slidably associated with adjacent corner sections mount the boom sections for movement relative to each other. A plurality of fluid pressure cylinder units located within the boom assembly are operable to selectively extend and contract the boom assembly by moving the boom sections relative to each other.

United States Patent Inventors Archer W Brown Minneapolis: James L. Montgomery. St. Paul; Lorraine V. Erkenbrack, St. Paul, all of Minn. App]. No. 833,079 Filed June 13, 1969 Patented Nov. 16, 197] Assignee American Hoist 8: Derrick Company Saint Paul, Minn.

EXTENSIBLE BOOM ASSEMBLY 25 Claims, 11 Drawing Figs.

US. Cl 308/3, 212/55, SOS/DIG. 8

InLCl .........Fl6c23/00, B66c 23/04 Field of Search. A .308/3, 36.],

| 56] References Cited UNITED STATES PATENTS 2,551,484 5/1951 Branning 29/483 3,243,236 3/l966 Grahams... 308/3 3,350,143 10/ l 967 Lichowsky 308/3 3,300,060 1/1967 Lado 212/55 3,304,136 2/1967 Muller 0. 308/36.l 3,445,004 5/1969 Grider et al 212/55 7 Primary Examiner-Martin P. Schwadron Assistant Examiner-Barry Grossman Allorney- Burd, Braddock & Bartz PATENTEnuuv 16 l97l iii M1 SHEET 2 [IF 4 FIE! E Arroxwzrs EXTENSIBLE BOOM ASSEMBLY BACKGROUND OF INVENTION Telescopic crane booms have been used on motor vehicles to provide heavy-duty mobile units. Most of the telescopic boom structures have a plurality of sections which move rela tive to each other to change the length of the boom. Hydraulic cylinders and cable and pulley mechanisms are used to move the boom sections relative to each other. Telescopic crane booms of this type are shown in U.S. Pat. Nos. 3,315,821 and 3,398,645. The box-type boom sections of these booms are not designed to utilize the maximum strength of the boom material. The loads on the boom sections are not evenly distributed to the corner portions of the sections. The corner portions of the boom sections are not reinforced and do not cooperate with bearing pads to accommodate the bending and twisting loads on the boom sections.

SUMMARY OF INVENTION The invention relates to a boom assembly having extensible boom sections that have maximum strength with a minimum weight. The boom sections have reinforcing corner members joined together with substantially flat plate members to form box-shaped boom sections. A plurality of boom sections are telescopically related relative to each other with a minimum clearance whereby they can contract and expand to change the length of the boom assembly. A contractable and extensible means located within the boom section is operable to move the boom sections relative to each other. The boom sections are slidably disposed relative to each other and are carried on longitudinally rockable wear and bearing pads which slidably engage adjacent corner members so as to provide direct and equalized load distribution on the boom sections.

An object of the invention is to provide high strength boom assembly sections that can be fabricated with accurate dimensional control of the depth and width of the sections so that they can telescope within each other with minimum clearances. A further object of the invention is to provide a boom section with the greatest amount of material at the corner portions where it offers the greatest resistance to combination downward and sideward bending forces and torsion. Another object of the invention is to rockably support comer portions of a boom section to distribute the load on the section.

IN THE DRAWINGS FIG. 1 is a side view of a truck-mounted boom hoist equipped with the boom assembly of the invention;

FIG. 2 is a rear end elevational view of FIG. 1;

FIG. 3 is a side view of the truck-mounted boom hoist showing the foreshortened boom assembly fully extended;

FIG. 4 is an enlarged foreshortened sectional view taken along line 4-4 ofFIG. 2;

FIG. 5 is an enlarged sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5;

FIG. 7 is an enlarged sectional view taken along line 7-7 of FIG. 6;

FIG. 8 is a sectional view taken along line 8-8 ofFIG. 4;

FIG. 9 is an enlarged sectional view taken along line 9-9 of FIG. 8;

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9; and

FIG. 11 is a longitudinal sectional view of a modified wear block.

Referring to the drawings, there is shown in FIGS. 1, 2, and 3, a truck 15 carrying an extensible boom hoist, indicated generally at 16. Truck 15 has an elongated longitudinal frame 17 connected to front and rear tandem dual wheels 18 and 19. A transport cab 21 is mounted on the front of the frame 17. The rear portion of the frame 17 carries a hoist support platform 22 mounting the hoist 16 for rotation about an upright axis. A power unit (not shown) operates to swing the entire hoist 16 relative to the platform 22 and truck 15.

As shown in FIG. 2, the truck 15 is laterally stabilized with two pair of outwardly directed arms 23 and 24 slidably attached to the midsection and rear of the frame 17. Downwardly directed jacks 26 and 27 are operatively connected to the outer ends of the arms 23 and 24 respectively. Each jack has a lower foot portion which engages the supporting surface to laterally stabilize the truck 15 and equalize and reduce the load on the tandem wheels 19.

The extensible boom hoist 16 has a supporting base 28 rotatably mounted on the platform 22 for movement about a generally upright axis. As shown in FIG. 2, laterally spaced upright side members or plates 29 and 31 are longitudinally secured to the top of base 28. Located adjacent the forward side of member 29 is a hoist cab 32 enclosing the controls for the hoist. Mounted on base 28 between the side members 29 and 31, laterally of the hoist cab 32, are a pair of winches 33 and 34 for receiving the cables or lines of the hoist.

A boom assembly, indicated generally at 36, is pivotally mounted with a transverse pivot member 37 to the upper rear portions of the side members 29 and 31. A hydraulic cylinder 38, operable to raise and lower the boom assembly 36, is connected to the midportion of the side members 29 and 31 with pivot structure 39. The piston rod of the cylinder 38 is connected with a pivot 41 to the boom assembly 36 forwardly of pivot 37.

Returning to FIGS. 1 and 3, the boom assembly 36 comprises a plurality of relatively movable boom sections, indicated generally at 42, 43, 44, and 45, which telescope relative to each other to change the length of the boom assembly. FIG. 1 shows the boom assembly 36 in a contracted transport position. FIG. 3 shows the boom assembly 36 in a fully extended and elevated position. The length of boom assembly 36 can vary between fully extended and fully contracted and the elevation angle can be changed up and down.

A head 46 connected to the outer end of boom section 45 carries a pulley assembly 47 for directing a line 48 to a load hook and pulley unit 49. A second pulled 51 directs a line 52 to a ball and hook member 53. The lines 48 and 52 extend over pulley assembly 54 along the top of the boom assembly 36 and are directed by pulleys 55 and 56 to the winches 33 and 34.

As shown in FIGS. 4 and 5, the first or base boom section 42 has a generally rectangular cross section and encloses the telescoped boom sections 43, 44, and 45. The boom section 42 has longitudinal right-angle corner members 57 at each corner extended the entire length of the boom section. Upright and parallel side plates 58 and 59 are attached to adjacent side angle members. In a similar manner, top plate 61 and bottom plate 62 are attached to the top and bottom angle members to form the elongated rectangular boom section. The right-angle corner members 57 are formed from rolled high strength steel as the bending and twisting forces on the boom section are maximum along the corners thereof. The side plates 58 and 59, top plate 61, and bottom plate 62 are smaller in thickness than the corner members. This construction places the greatest amount of metal in the corners of the boom section where it offers the greatest resistance to vertical and lateral bending forces and to torsion forces. The rightangle comer members 57 are characterized as being strong and fabricated from high strength metal capable of withstanding large bending and twisting forces. The plates can be of the same metal as the corner members.

As shown in FIG. 9. right-angle member 57 has inwardly directed steps 63 along the outer ends of the flanges of the angle member. The steps 63 have outwardly directed bevel edges 64. Both steps 63 and bevel edges can be rolled into the angle member during fabrication thereof. The edges of the plates are located in the steps. The beveled edges 64 provide linear spaces for welds 66 securing the plates to the angle members. The cross-sectional dimensions of the boom section is held to close tolerances as the steps 63 and welds 66 allow for variations in the width of the plates. The lapping of the plates and comer members at the steps 63 adjacent the bevel edges 64 provide a continuous groove for the weld 66 whereby minimum welding is needed to secure the plates to the comer members.

ment of the boom sections and transmit the lateral deflection and twisting forces to the corner members.

The outer ends of each boom section 42, 43, and 44 are reinforced with U-shaped collars 67, 67B, and 67C. The collar 67, shown in FIG. 6, comprises an inwardly directed channel member secured to the side plates 58 and 59, bottom plate 62 and the corner angle members 57.

As shown in FIGS. 4, 5, and 6, a pair of bottom wear pads or bearing blocks 68 slidably support the second boom section 43 in the base boom section 42. Bottom wear pads 68 are lower flanges of the right-angle corner members of the boom sections.

Referring to H6. 6, the wear pads 68 are held in assembled relationwith the corner angle members 57 with generally flat U-shaped retainers 73 welded to the top of the horizontal flanges of the corner members 57. The wear pads 68 are located between the retainer and the upright flanges of the corner members. As shown in FIG. 7, the wear pad 68 has a made from plastic material, as laminated phenolic, rethane or metal, as ductile iron. The wear pads 68 with their top sliding faces 74 in conjunction with the convex supporting surface 76 provide limited rocking action for the supporting boom section. This action equalizes the bearing pressure under all conditions of boom assembly loading and deflection. Returning to FIG. 4, the inner top ends of the boom sections 43, 44, and 45 carry pairs of top wear pads 77, 78, and 79 located in sliding engagement with the right-angle corner members of the adjacent boom sections. The wear pads 77, 78, and 79 are identical in structure to the bottom wear pads 68.

As shown in FIG. 8, wear pads 77, positioned adjacent the inner ends of the corner angle members 57B, are located in generally U-shaped retainers 81 secured to the top corner U-shaped boom section 44. Cylinder unit 94 comprises a cylinder 96 having a rod end collar 97 secured to an inner end frame 98 of cylinder 96 in general longitudinal alignment with the boom sections.

Positioned above the second hydraulic cylinder unit 94 is a third hydraulic cylinder unit 103 comprising a cylinder 104 having a rod end collar 106 secured to the inner end frame 107 of the outer boom end of the cylinder unit is returned through an outlet line 113 to a reservoir.

A second cylinder inlet line 114 couples the head end of cylinder unit with the head end of cylinder 94. A return line 116 connects the rod ends of cylinders 85 and 94. In a similar manner, a third cylinder inlet line 117 connects the head ends of cylinders 94 and 103. A third cylinder outlet line 118 connects the rod ends of cylinders 94 and 103. This hydraulic system of the first, second, and third cylinder. units is operable sembly 36 can be sequentially extended by utilizing mechanical latches or hydraulic brakes or other holding structures (not shown) to sequentially extend the boom assembly. For example, the third and fourth boom sections 44 and 45 can be locked together until the second boom section 43 is fully extended relative tothe first boom section 42. At this time, the third boom section will be released from the second boom sec- In use, the boom sections 42 to 45 telescope relative to each other in response to the operation of the extensible and contractable means 84. The boom sections slide on the pairs of wear pads which ride on the corner members of the boom sections. The lower wear pads 68, 69, and 71 function as support and fulcrum members which transmit force through the comer members. These wear pads have longitudinally convex bottom surfaces which permit the wear pads to adjust for the deflection and twist of the boom sections under load. Since the wear pads are directly on the corner sections, loads are transmitted to the comer sections of the interrelated boom sections.

The top pairs of wear pads 77, 78, and 79 function as sliding stop members. These wear pads also act on the corner members of the boom sections and have longitudinal convex bottom surfaces so that the wear pads can adjust for the deflection and twisting of the boom sections and transmit the loads to the corner sections. The lateral bending and twisting forces are transmitted to the side-by-side corner members.

This combination of corner member and connecting plate structure produces a boom section that has a maximum strength per unit weight of material and permits the maximum amount of deflection and twisting without interference with the operation of the boom assembly.

An alternate construction of the wear block, shown in FIG. 11, is indicated at 120. Block 120 has a base 121 with a longitudinal convex outer surface 122. Base 121 is made of metal, as steel, or similar hard material. The side opposite the surface 122 has a rectangular recess 123 carrying a flat pad 124 of plastic material or similar antifriction material. The pad 124 is bonded to the base 121 to keep the pad in assembled relation with the base. The top surface 126 of the pad 124 is a flat sliding surface.

The invention, as described and shown, includes changes in size and materials of the construction members. The boom sections may have other cross-sectional shapes, as hexagonal, octagonal and the like. The bearing pads may have sphericalshaped supporting bottom faces. Other changes may be made without departing from the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A boom assembly comprising: a plurality of telescopic arranged boom sections, each boom section having an elongated right-angle member at each corner thereof, each angle member being a rolled member having generally normally disposed flanges, each flange having an elongated inwardly directed linear step along the outer end thereof forming an elongated linear pocket, elongated plates extended between adjacent angle members forming the sides, top, and bottom of the boom section, said plates having linear side portions located in the pockets in the flanges, attaching means securing the side portions of the plates to the flanges. and wear pad means located between and only in engagement with the corner members of the adjacent boom sections.

2. The boom assembly of claim 1 wherein: the attaching means comprise linear welds to secure the corner members to the plates.

3. The boom assembly of claim 2 wherein: each comer flange has an outwardly directed bevel edge providing a groove for the weld.

4. The boom assembly of claim 2 wherein: said linear welds are located in the steps used to secure the corner members to the plates.

5. The boom assembly of claim 1 wherein: each corner member has a thickness greater than the thickness of the plates.

6. The boom assembly of claim 1 wherein: the wear pad means comprise block members, each block member having a flat surface in sliding surface contact with one comer member and a convex face opposite the flat surface in engagement with the other corner member.

7. The boom assembly of claim 6 including: retaining means secured to said other corner member to confine the block member for limited rocking movement on the other corner member.

8. The boom assembly of claim 1 wherein: the wear pad means comprise a first pair of wear pads located between and in engagement with the lower corner members and a second pair of wear pads located between and in engagement with the upper comer members.

9. The boom assembly of claim 8 wherein: each wear pad has a flat surface in sliding surface contact with a movable comer member and a longitudinally convex face opposite the flat face surface in engagement with the other corner member.

10. The boom assembly of claim 9 including: retaining means secured to the comer member to confine the wear pad for limited rocking movement on the other corner member.

11. A boom assembly comprising: a plurality of telescopic arranged boom sections, each boom section having an elongated linear corner member at each corner thereof, each member having generally normally disposed portions, each portion having an elongated inwardly directed linear step along the outer end thereof forming an elongated linear pocket, and elongated plate means having edges extended generally parallel to and adjacent the corner members, said edges located in the pockets in the portion, attaching means for securing said edges to the adjacent portions of the corner members, and wear pad means located between and only in engagement with the corner members of adjacent boom sections.

12. The boom assembly of claim 11 wherein: said attaching means to secure the plate means to the corner members comprise linear welds located in the steps to secure the corner members to the plate means.

13. The boom assembly of claim 11 including: collar means surrounding at least a portion of each boom section and secured to the corner members and the plate means of the boom section.

14. The boom assembly of claim 11 wherein: each corner member has a thickness greater than the thickness of the plate means.

15. The boom assembly of claim 11 wherein: said wear pad means comprises block means having a flat surface in sliding surface contact with one corner member and a convex face opposite the flat face in rocking engagement with the corner member adjacent the one corner member.

16. The boom assembly of claim 15 wherein: the block means has a convex face curved in the direction of movement ofone ofthe corner members.

17. The boom assembly of claim 16 wherein; the block means is made of plastic material, and said convex face has a relatively large radius ofcurvature as compared to the longitudinal length of the block means.

18. The boom assembly of claim 15 wherein: said block means comprises a hard base member having a convex surface and pad means having a flat sliding outer surface, said pad means being secured to the base member o posite the convex surface.

19. The boom assembly of claim 15 including: retaining means secured to one corner member for holding the block means on the one corner member.

20. The boom assembly of claim 19 wherein: the retaining means comprise a generally U-shaped member located adjacent three sides of the block means.

21. The boom assembly of claim 1 wherein: said wear pad means comprises block means having a flat surface adapted to be located in sliding contact with one corner member and a convex face curved in the direction of movement of one of the comer members opposite the flat surface in engagement with the comer member adjacent the one corner member.

22. The boom assembly of claim 21 wherein: the block means is' made of hard plastic material and said convex face has a relatively large radius of curvature compared to the length of the block means.

23. The boom assembly of claim 21 wherein: said block means comprises a hard base member having a convex surface 7 8 and pad means having a flat sliding outer surface, said pad means on said one corner member. means being secured to the base member opposite the convex h boom as e bly of l im 24 wh rein: the retaining surface. means comprises a generally U-shaped member located ad- 24. The boom assembly of claim 21 including: retaining jacem three Sides Ofthe block means secured to one comer member for holding the block 5 

1. A boom assembly comprising: a plurality of telescopic arranged boom sections, each boom section having an elongated right-angle member at each corner thereof, each angle member being a rolled member having generally normally disposed flanges, each flange having an elongated inwardly directed linear step along the outer end thereof forming an elongated linear pocket, elongated plates extended between adjacent angle members forming the sides, top, and bottom of the boom section, said plates having linear side portions located in the pockets in the flanges, attaching means securing the side portions of the plates to the flanges, and wear pad means located between and only in engagement with the corner members of the adjacent boom sections.
 2. The boom assembly of claim 1 wherein: the attaching means comprise linear welds to secure the corner members to the plates.
 3. The boom assembly of claim 2 wherein: each corner flange has an outwardly directed bevel edge providing a groove for the weld.
 4. The boom assembly of claim 2 wherein: said linear welds are located in the steps used to secure the corner members to the plates.
 5. The boom assembly of claim 1 wherein: each corner member has a thickness greater than the thickness of the plates.
 6. The boom assembly of claim 1 wherein: the wear pad means comprise block members, each block member having a flat surface in sliding surface contact with one corner member and a convex face opposite the flat surface in engagement with the other corner member.
 7. The boom assembly of claim 6 including: retaining means secured to said other corner member to confine the block member for limited rocking movement on the other corner member.
 8. The boom assembly of claim 1 wherein: the wear pad means comprise a first pair of wear pads located between and in engagement with the lower corner members and a second pair of wear pads located between and in engagement with the upper corner members.
 9. The boom assembly of claim 8 wherein: each wear pad has a flat surface in sliding surface contact with a movable corner member and a longitudinally convex face opposite the flat face surface in engagement with the other corner member.
 10. The boom assembly of claim 9 including: retaining means secured to the corner member to confine the wear pad for limited rocking movement on the other corner member.
 11. A boom assembly comprising: a plurality of telescopic arranged boom sections, each boom section having an elongated linear corner member at each corner thereof, each member having generally normally disposed portions, each portion having an elongated inwardly directed linear step along the outer end thereof forming an elongated linear pocket, and elongated plate means having edges extended generally parallel to and adjacent the corner members, said edges located in the pockets in the portion, attaching means for securing said edges to the adjacent portions of the corner members, and wear pad means located between and only in engagement with the corner members of adjacent boom sections.
 12. The boom assembly of claim 11 wherein: said attaching means to secure the plate means to the corner members comprise linear welds located in the steps to secure the corner members to the plate means.
 13. The boom assembly of claim 11 including: collar means surrounding at least a portion of each boom section and secured to the corner members and the plate means of the boom section.
 14. The boom assembly of claim 11 wherein: each corner member has a thickness greater than the thickness of the plate means.
 15. The boom assembly of claim 11 wherein: said wear pad means comprises block means having a flat surface in sliding surface contact with one corner member and a convex face opposite the flat face in rocking engagement with the corner member adjacent the one corner member.
 16. The boom assembly of claim 15 wherein: the block means has a conveX face curved in the direction of movement of one of the corner members.
 17. The boom assembly of claim 16 wherein: the block means is made of plastic material, and said convex face has a relatively large radius of curvature as compared to the longitudinal length of the block means.
 18. The boom assembly of claim 15 wherein: said block means comprises a hard base member having a convex surface and pad means having a flat sliding outer surface, said pad means being secured to the base member opposite the convex surface.
 19. The boom assembly of claim 15 including: retaining means secured to one corner member for holding the block means on the one corner member.
 20. The boom assembly of claim 19 wherein: the retaining means comprise a generally U-shaped member located adjacent three sides of the block means.
 21. The boom assembly of claim 1 wherein: said wear pad means comprises block means having a flat surface adapted to be located in sliding contact with one corner member and a convex face curved in the direction of movement of one of the corner members opposite the flat surface in engagement with the corner member adjacent the one corner member.
 22. The boom assembly of claim 21 wherein: the block means is made of hard plastic material and said convex face has a relatively large radius of curvature compared to the length of the block means.
 23. The boom assembly of claim 21 wherein: said block means comprises a hard base member having a convex surface and pad means having a flat sliding outer surface, said pad means being secured to the base member opposite the convex surface.
 24. The boom assembly of claim 21 including: retaining means secured to one corner member for holding the block means on said one corner member.
 25. The boom assembly of claim 24 wherein: the retaining means comprises a generally U-shaped member located adjacent three sides of the block means. 